In certain medical procedures, such as blood vessel embolization, it is desired to inject particles into the body. The procedure is a minimally invasive alternative to surgery. The purpose of embolization is to prevent blood flow to an area of the body, which effectively can shrink a fibroid, such as a uterine fibroid. It can also shrink a tumour or block an aneurysm. It is typically done by injecting blocking particles into a blood vessel.
The procedure is carried out as an endovascular procedure by a radiologist in an interventional suite. It is common for most patients to have the treatment carried out with little or no sedation, although this depends largely on the organ to be embolized.
Access to the organ in question is acquired by means of a guidewire and catheter. The position of the correct artery or vein supplying the undesired tissue in question is located by X-Ray images. These images are then used as a map for the radiologist to gain access to the correct vessel by selecting an appropriate catheter and or wire, depending on the shape of the surrounding anatomy
The blocking particles are mixed into a saline solution, sometimes a contrast agent is added (to make the solution opaque to X-Rays). The blocking particles have to be of certain sizes, typically between 0.1 mm to 1 mm, in order to block the blood vessel at the right diameter. Such particles tend to settle very quickly out of the solution as they are heavier than water, causing an uneven concentration of particles during the injection. The settling occurs in as little as a few seconds. It is inconvenient to keep shaking the syringe used for injection, as the whole process is performed in a few seconds and the doctor has to concentrate on injecting the correct amount. It is desired to have a syringe that can keep the particles uniformly dispersed in the saline solution regardless of delays in the injection process or speed of the injection. Since the syringes used are low cost disposable items, it is desired that the device used to keep the particles uniformly dispersed will also be very low cost and disposable. The ideal mixing syringe needs the following attributes:
A. Ability to be re-filled multiple times during a procedure. This rules out any single-use designs, typically using the rupturing of a membrane to allow mixing.
B. Generate a strong mixing action, preferable by creating a vortex in the mixture.
C. Use the minimum modification to a standard syringe.
Prior art mixing syringes, such as disclosed in U.S. Pat. No. 7,883,490 are designed to mix together two materials stored separately in two compartments. They are not designed to stir up a pre-mixed solution. Prior art syringes designed to stir-up embolization mixtures, such as disclosed in US2009/0247985, are needlessly complex. Also, many of the prior art mixing syringes are not designed to be filled with the pre-mixed solution just before use. This is required during embolization, as the correct volume and ratio of saline, particles and contrast agent has to be customized to the procedure by the doctor. The current invention acts as a regular syringe, allowing filling and injecting at any time, but it keeps the solution stirred up during injection. Similar to a regular syringe, it can be re-used several times during a procedure, if more particles have to be injected. The invention can be manufactured out of a regular syringe, which is a very low cost item.